OnCollision and AddForce

I started with a simple task: To have a steadily bouncing ball.

However with bounciness set to 1 that ball keeps bouncing higher and higher.

So I added this to the OnCollision:

rigidbody.AddForce(0,Toolbox.Instance.maxBounceHeightIdle - collision.relativeVelocity.y,0,ForceMode.VelocityChange);

Where Toolbox.Instance.maxBounceHeightIdle is a static value, in this case 5.

This works as expected and I can now apply input to the ball, moving it along x axis by adding force as necessary and the y bounce always stays in that 5 limit range.

The problem arises when I collide with something that is vertically. It seems that I am getting the wrong values in collision.relativeVelocity and suddenly the ball bounces very high.

Any pointers?

Here is a video of what I mean. It's that huge bounce near the end that bothers me:

http://gfycat.com/AchingVeneratedHochstettersfrog

 

I suck at math. I think this fixed it:

if(collision.relativeVelocity.y > 0)
rigidbody.AddForce(0, Toolbox.Instance.maxBounceHeightIdle - collision.relativeVelocity.y, 0, ForceMode.VelocityChange);